132 PROCEEDINGS OF SOCIETIES. 



by metamorphic action. It can scarcely be ranked among the va- 

 rieties, for every part of the limestone has been alike affected by 

 it In the bottom, the calciferous slate on the shore immediately 

 west of the pier at Howth is changed into a dolomitic condition. At 

 the top, the limestone at the summit of Belmore mountain, in Ferma- 

 nagh, is a Dolomite. The general colour of it is a yellowish-brown, 

 but it varies. At Bagenalstown in Carlow it is quite black. It is 

 extensive about Ballyshannon, in the vicinity of the hill of mica slate, 

 which appears to have been protruded through the limestone there. It 

 is usually found in connexion with, or in the vicinity of, great faults in 

 the strata, and sometimes it is the matter which fills up a dyke. A case 

 of this latter kind is observed on the shore, about a furlong north of the 

 Martello Tower at Portmarnock, in the county of Dublin, where a dis- 

 tinct vertical dyke of this substance is protruded through ordinary lime- 

 stone strata. Another appears at Dangan, on the shore a mile north of 

 Eush, in this county also. 



I have now brought my subject to a conclusion, and will only fur- 

 ther say, that to Mr. Griffith we owe much. If another man had been 

 employed in the public capacity that he filled in this country, we proba- 

 bly never would have the " Geological Map" of Ireland now before us; 

 and though it has some faults to be corrected, yet it exists a monument 

 of a great love for his favourite pursuit, joined to a good opportunity of 

 carrying it into effect; and though I differ with him on the subject of 

 this paper, we know that the education of men, and the means by which 

 they attain their knowledge, are so very different that it is impossible 

 they could all think alike. 



On the Calp as a geological subdivision, or band of rock, I have not 

 any of the writings of Professor Sedgwick or Sir Henry de la Beche, 

 to quote in corroboration of my views, as I had when treating of the 

 Devonian System, or the Old Eed Sandstone of Herefordshire. The Calp 

 has been written upon only by Mr. Griffith, and no views but his are 

 yet published on the subject. There are, however, a few sentences in 

 Professor Sedgwick's Introduction, already mentioned, which are so ap- 

 plicable to the present case that I shall quote them. He says : — 



" In the progress of a rapidly advancing science, a great and good 

 workman may make a great mistake ; and if that mistake be largely 

 adopted under the sanction of his name, so much the worse for himself. 

 A bold generalization, ratified by a technical name, may have the pro- 

 mise of some endurance ; for men hate to be dangling in doubt, and one 

 who offers to the inquiring mind an apparent resting-place is sure of 

 immediate favour. When a man has accepted a technical name, he never 

 readily submits to the humiliation of parting with it ; and he will often 

 cling to names with more tenacity than he clings to principles, which 

 he never, perhaps, examined for himself, or, it may be, never thoroughly 

 comprehended. 



" The truths of nature, however, are not things mutable, and depen- 

 dent on popular voice ; they are eternal. Physical mistakes, whether 

 of classification and nomenclature, or of a false induction from facts im- 



